Load balancer

ABSTRACT

A LOADING BALANCER ASSEMBLY OF THE TYPE USING A COUNTERWEIGHTED PARALLELOGRAM LINKAGE WHEREIN THE LOAD CARRYING ARMS INCLUDE AN OFFSET PORTION TOGETHER WITH MEANS FOR APPLYING A FORCE TO ONE OF THE ARMS THAT IS SUFFICIENT TO PRECLUDE CREEPING MOVEMENT OF THE LOAD CARRYING ARM HAVING THE OFFSET PORTION DUE TO THE PRESENCE OF THE OFFSET PORTION THEREIN.

Oct. 26, 1971 N. G. GOUDREAU LOAD BALANCER 2 Shoots-Shut z Filed March 19, 1969 FULC'FUM Nil/WA:

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United States Patent 3,615,067 LOAD BALANCER Noel G. Goudreau, Mendota, Ill., assignor to Conco, Inc. Filed Mar. 19, 1969, Ser. No. 808,424 Int. Cl. A47f 5/00 US. Cl. 248-325 8 Claims ABSTRACT OF THE DISCLOSURE A loading balancer assembly of the type using a counterweighted parallelogram linkage wherein the load carrying arms include an offset portion together with means for applying a force to one of the arms that is sufficient to preclude creeping movement of the load carrying arm having the offset portion due to the presence of the offset portion therein.

BACKGROUND OF THE INVENTION In US. Pat. No. 3,402,911 to ONeill there is disclosed a loading balancer wherein the load bearing arm includes an offset portion so that the balancer may be used to move tools, dies or other types of loads around an obstruction that would otherwise prevent delivery of the work held by the balancer to a desired location. The ONeill balancer works extremely well for its intended purpose but the presence of the offset in the load bearing arm results in a somewhat shifted location of the center of gravity thereof which can occasionally result in some creeping movement of the arm. While quite often such creeping of the load bearing arm can be tolerated, in some cases, it is undesirable and the instant invention provides means for preventing such creeping movement.

SUMMARY OF THE INVENTION This invention relates to a loading balancer assembly wherein four arms are utilized to form a parallelogram linkage with one of the arms including a downward, load bearing extension having an offset portion so that the load can be moved around obstructions. Another of the arms is counterbalanced and pivotally mounted on a standard so that the overall linkage can be pivoted to raise or lower the load. Furthermore, the load bearing arm may be moved from side to side. To provide balancing for the load, a hydraulic cylinder may be used as a force a plying means to one of the arms if the same is coupled thereto by a connection that will permit relative horizontal movement therebetween.

According to the invention, a spring reel having a spring loaded cable extending therefrom is mounted in such a way that the cable may extend to one of the arms to apply a generally horizontal force thereto, which force provides a moment which is equal and opposite to a moment provided by the offset center of gravity of the load bearing arm due to the offset therein. As a result, the forces tending to cause the load bearing arm to creep are balanced out by the spring reel tension and the arm will not creep.

Other objects and advantages of the invention will become apparent from the following specification taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a loading balancer assembly embodying the invention;

FIG. 2 is a fragmentary, enlarged side elevation illustrating force applying means provided in the balancer assembly according to the invention; and

FIG. 3 is a schematic illustrating the static vectors involved in the invention.

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DESCRIPTION OF- THE PREFERRED EMBODIMENT An exemplary embodiment of a balancer made according to the invention is illustrated in FIG. 1 and is seen to be supported from an overhead track 10 by means of a trolley 11 having supporting wheels 12 and 13 engaged with the track. A hanger 14 depends from the trolley 11 and has a pair of spaced depending arms 15 (only one of which is shown) which are each formed of a pair of spaced apart plates. Mounting bracket extends from a location between the upper ends of the arms 15 to mount pivotally, a fluid cylinder 21 having a piston rod 22 connected by a pin 23 to a pair of spaced apart side plates 24 (only one of which is shown), with the pin 23 extending transversely therebetween. The degree of extension of the piston rod 22 from the cylinder 21 determines the elevation of the side plates 24 relative to the hanger arms 15 and thereby the angle of the parallelogram linkage to be described. The plates 24 are guided for up and down movement and resultantly guide the piston rod 22 by means of an upper set of rollers and a lower set of rollers 32 which travel in elongate guide slots 34 in the side plates 24. These rollers are all fixedly mounted on the hanger arms 15 with the upper pair of rollers 30 being rotatably mounted on pins connected to the hanger arms 15 and the lower rollers 32 being rotatably mounted on a pin 42 extending through the lower end of the hanger arms 15.

The loading balancer assembly includes a first tubular arm pivotally connected by pivot pin 51 to the hanger arms 15. This first arm carries a counterweight 52 at one end and, at the other end, has a pivot connection at 53 to a second arm, which is the work-supporting arm indicated generally at 54. A third arm 55 extends parallel to the first arm 50 and is pivotally connected at 56 to the second arm 54. The opposite end of the arm 55 rotatably mounts a follower shaft 57 having rollers 58 at opposite ends thereof and spaced beyond the arm 55 which engage in tracks 59 extending generally horizontally in the side plates 24. With this construction, force exerted on the side plates by the fluid cylinder 21 is transmitted to the third arm 55 of the parallelogram linkage to the tracks 59 engaging rollers 58. This force applied to the follower shaft 57 is transmitted to a fourth arm of the parallelogram linkage to the first arm 50. This fourth arm comprises a pair of spaced links (only one of which is shown) which receive at their lower ends the follower shaft 57 and at their upper ends carry a link pin 67 which pivotally connects to the first arm 50.

The work support arm 54 carries a work holding fixture 70 at its lower end for engaging a workpiece 73 shown in broken lines. The fixture 70 is pivotally mounted at 74 to the lower extremity of the work support arm 54. Other fixtures, including a swivel hook, could be used.

As is known in the art, a load held by fixture 70 can be balanced to provide for easy manual manipulation thereof by controlling the amount of pressure applied to the cylinder 21 which, because of the construction including the parallelogram linkage, would cause constant balancing of the load in any of the range of positions for the loading balancer.

As described in the above identified ONeill patent, a feature of the work-support arm 54 is to further increase the utilization of the loading balancer by forming the worksupport arm in two parts with an upper part having the pivot connections 53 and 56 to the first arm 50 and the third arm '55 and a lower part 81 carrying the pivot connection 74 for the work fixture 70. The lower part 81 has a bend therein to permit positioning of the lower arm part 81 relative to an obstruction such as, for example,

placing the workpiece underneath an overhang such as the head of a machine tool or a table. The work load is substantially balanced, at all times, because the pivot connection 74 for the work fixture lies in a straight line defined by the pivot connections 53 and 56. However, while the arrangements described thus far provide for substantial balancing at all times, it will be appreciated that the analysis neglects the efiect of the weight of the arm 54, and more particularly, the location of the center of the gravity of the same due to the offset or bend in the lower arm part 81. That is, because of such an offset, the center of gravity of the arm 54 will not lie in the line defined by the pivots 53, 56 and 74 but rather, as viewed in FIG. 1, will lie somewhat to the right thereof. As a result, as the pivot 53 is a fulcrum point, it will be appreciated that the arm 54 will tend to pivot in a clockwise direction about the point 53 due to a moment comprised of the product of the weight of the arm 54 and the distance of the center of gravity of the same from the line defined by the pivots 53, 56 and 74.

To counterbalance this moment, force applying means are provided to provide an equal and opposite moment about the pivot point 53 and such means may be best understood with reference to FIG. 2.

A spring reel 90 of conventional construction is mounted on a pivot 92 and has a wire rope cable 94 extending therefrom, the latter being spring loaded as is well-known in the art. A rotatable sheave 96 is mounted on one of the side plates 24 by any suitable means adjacent the ends of the slots 59 and the cable 94 is passed about the same and then secured to the third arm 55 by a nut or other suitable fastener 98 associated with the pivot point 57. As a result, as viewed in FIG. 2, the spring reel 90 will cause a force to be applied to the third arm 55 in a generally horizontal direction, which force will act towards the right as viewed in FIG. 2. For all practical purposes, the applied force is constant for all positions of the pivot point 57 in slot 59.

The magnitude of the force that must be applied by the spring reel 90 to the third arm 55 can best be understood from a consideration of FIG. 3 which indicates in schematic form, the various vectors and moments involved. As seen, the work-support arm 54 includes an offset portion in the lower arm portion 81 so that the center of gravity of the arm is at a point 100 also designated by the legend CG. The force of gravity acting on the center of gravity at the point 100 provides a force acting in the direction of an arrow 102 and designated F which force is spaced from the line defined by the pivot points 53, 56 and 74 by a distance designated D As a result, considering the pivot point 53 as a fulcrum, it will be appreciated that a moment tending to rotate the arm 54 in a clockwise direction around the point 53 exists and the same moment, designated M is equal to the product of the downward force or weight of the arm F and the distance D From the foregoing description of the spring reel 90 and appurtenances thereto, it will be appreciated that a force F is also acting at the pivot point 57 which will be applied to the pivot point 56 thru the third arm 55. The point of action of the force F is separated from the fulcrum point 53 by a distance D, and the product of the force F and D will provide a moment M tending to rotate the arm 54 in a counterclockwise direction about the point 53.

As pointed out previously, it is the principal object of the invention to eliminate any creepage in the arm 54 due to the presence of the olfset and lower arm portion 81 and to this end, the clockwise moment M must be equal to the counterclockwise moment M so that the product of the force F and the distance D must equal the product of the force F and the distance D Since the weight of the arm, or F is known, and the distance D can be easily ascertained, and the distance D is known, it will be appreciated that the force F to be applied by the spring reel 90 to attain a static condition is equal to the product 4 of F times the ratio of D :D Thus, by selecting a spring reel to provide a force F as determined by F D and D in the foregoing manner, creeping movement of the arm 54 due to the offset in the lower arm portion 81 may be eliminated.

From the foregoing, it will be appreciated that the force applying means provided in the form of the spring reel 90 in effect act upon the work supporting arm by virtue of the interconnection by the cable 94 to the third arm 55 which, in turn, is connected. to the second, or work supporting arm 54. Of course, if desired, a force could be applied to the second arm 54 by suitable connections other than those shown. However, the illustrated construction is preferred to the extent that the force applying means may be made relatively compact with respect to the remainder of the balancing.

Having described a specific embodiment of my invention as required by 35 U.'S.C. 112, I do not wish to be limited to the details set forth, but rather, to have the same construed broadly as set forth in the following claims.

I claim:

1. In a loading balancer assembly including a mount having a base member; a generally horizontal first arm pivotally mounted on said base member for rotation about a generally horizontal axis; a generally vertical second arm adapted to receive a load to be hoisted and balanced by said assembly, said second arm being pivotally connected to one end of said first arm and including an offset portion between its ends; a third arm pivotally connected to said second arm; and a fourth arm pivotally connected at one end to said first arm and at its other end to said third arm, said arms between said pivotal connections forming a parallelogram; and a counterweight operatively connected to one of said arms; the improvement comprising: means for applying a force to one of said arms to produce a torque substantially equal and opposite to the torque produced by the weight of the offset portion of the second arm.

2. A load balancer assembly according to claim 1 wherein said force applying means is connected to one of said arms to apply the force in a generally horizontal direction.

3. A load balancer assembly according to claim 2 wherein said force applying means is connected to said third arm.

4. A load balancer assembly according to claim 1 wherein said force applying means comprises spring means.

5. A load balancer assembly according to claim 4 wherein said spring means comprises a spring reel affixed to said base member and having a spring loaded cable extending therefrom to one of said arms.

6. A load balancer assembly according to claim 5 wherein said cable is connected to said third arm; and roller means interposed between said spring reel and said third arm and engaging said cable so that said cable extends from said roller means to said third arm in a generally horizontal direction.

7. In a loading balancer assembly including a mount having a base member; a generally horizontal first arm pivotally mounted on said base member for rotation about a generally horizontal axis; a generally vertical second arm adapted to receive a load to be hoisted and balanced by said assembly, said second arm being pivotally connected to one end of said first arm and including an oifset portion between its ends; a third arm pivotally connected to said second arm; and a fourth arm pivotally connected at one end to said first arm and at its other end to said third arm, said arms between said pivotal connections forming a parallelogram; a counterweight operatively connected to one of said arms; means for applying a generally vertical force to said third arm; and means interconnecting said third arm and said generally vertical force applying means to allow relative horizontal movement therebetween; the improvement comprising: a means for applying a force to said second arm to produce a torque substantially equal and opposite to the torque produced by the weight of the offset portion of the second arm, said last named force applying means comprising spring means.

8. A loading balancer according to claim 7 wherein said interconnecting means comprises at least one plate extending adjacent said base member and including a generally horizontal guide slot, to receive a roller carried by both said third and fourth arms; and said spring means includes a spring reel secured to said plate and having a spring loaded cable extending therefrom, a sheave mounted on said plate adjacent one end of said guide slot, said cable being trained about said sheave from said spring reel and secured to the pivotal connection between said third and fourth arms.

References Cited UNITED STATES PATENTS 218,210 8/1919 Alling et al 248-281 2,090,439 8/1937 Carwardine 248-325 x 2,200,518 5/1940 Perbal 248280 2,665,870 1/1954 De Wiess 248280 3,003,737 10/1961 Mehr 248-280X 3,402,911 9/1968 ONeill 248-325 FOREIGN PATENTS 772,510 11/1954 Great Britain 248-117.1

WILLIAM H. SCHULTZ, Primary Examiner 

